add log flag

go.mod

@@ -4,6 +4,7 @@ go 1.13
 
 require (
 	github.com/gdamore/tcell v1.3.0
+	github.com/mitchellh/go-homedir v1.1.0
 	github.com/rivo/tview v0.0.0-20191018125527-685bf6da76c2
 	golang.org/x/crypto v0.0.0-20191029031824-8986dd9e96cf
 )

go.sum

@@ -8,6 +8,8 @@ github.com/lucasb-eyer/go-colorful v1.0.2 h1:mCMFu6PgSozg9tDNMMK3g18oJBX7oYGrC09
 github.com/lucasb-eyer/go-colorful v1.0.2/go.mod h1:0MS4r+7BZKSJ5mw4/S5MPN+qHFF1fYclkSPilDOKW0s=
 github.com/mattn/go-runewidth v0.0.4 h1:2BvfKmzob6Bmd4YsL0zygOqfdFnK7GR4QL06Do4/p7Y=
 github.com/mattn/go-runewidth v0.0.4/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
+github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
+github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
 github.com/rivo/tview v0.0.0-20191018125527-685bf6da76c2 h1:GVXSfgXOMAeLvFH7IrpY3yYM8H3YekZEFcZ14q9gQXM=
 github.com/rivo/tview v0.0.0-20191018125527-685bf6da76c2/go.mod h1:/rBeY22VG2QprWnEqG57IBC8biVu3i0DOIjRLc9I8H0=
 github.com/rivo/uniseg v0.1.0 h1:+2KBaVoUmb9XzDsrx/Ct0W/EYOSFf/nWTauy++DprtY=

main.go

@@ -2,15 +2,44 @@ package main
 
 import (
 	"encoding/json"
+	"flag"
 	"fmt"
 	"io/ioutil"
 	"log"
 	"os"
+	"path/filepath"
 
+	"github.com/mitchellh/go-homedir"
 	"github.com/skanehira/tson/gui"
 	"golang.org/x/crypto/ssh/terminal"
 )
 
+var (
+	enableLog = flag.Bool("log", false, "enable log")
+)
+
+func init() {
+	flag.Parse()
+	if *enableLog {
+		home, err := homedir.Dir()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+
+		logWriter, err := os.OpenFile(filepath.Join(home, "tson.log"), os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+
+		log.SetOutput(logWriter)
+		log.SetFlags(log.Lshortfile)
+	} else {
+		log.SetOutput(ioutil.Discard)
+	}
+}
+
 func run() int {
 	if !terminal.IsTerminal(0) {
 		b, err := ioutil.ReadAll(os.Stdin)